[guidoc]

First time Tig, first time posting.

I work in a small job shop. I usually MIG simple fixtures and repairs. We've got some racking to make for ourselves, and I decided it would be a good place to learn some TIG since we've got the machine.

The material is structural steel C channel. The plan is to tack everything, then go back and weld the beads once everything is fit up. I'm having a couple of issues

- the welds are orange/gold in color. Is this normal for TIG?
- There's lots of soot around the weld. Normal for TIG welding structural steel with scale? I also started prepping the scale off and got the same soot. Maybe not related?
- Some of the weld has pock marks and craters where I ended the tack. I've been trying to slowly let off the pedal and hold the torch to the weld, but I haven't been able to get rid of the blemishes. Any suggestions on this?

Machine: Miller Syncrowave 350 LX
Gas: straight argon
Tungsten: 3/32 red tip
Filler: ER70S-2

[Artie F. Emm]

Welcome, GuidoC! The TIG process should give off no sparks and no smoke when everything is going right: that means starting your weld on shiny bare metal, with no scale, paint, residual oil, or contaminants of any kind. The soot and discoloration you mention can be due to poor gas coverage: what is your flow rate?

The pock marks and craters may be caused by the mill scale: try removing it completely, then wiping down the weld area with acetone to remove surface contaminants. In your photos the end of the clamp and the swivel pad are hidden inside the channel: you probably need to remove mill scale from the two surfaces that are touching, as well.

I once welded up a broken lawn mower handle, and used TIG just for the practice and seat time. I used a piece of electrical conduit as a sleeve to connect the two broken ends. I ground off the galvanizing on the outside but not on the inside, and when I stopped the arc the weld would just barf out all the galvanizing from the inside of the conduit. It must have been migrating from the inside of the sleeve tube, through the weld to the outside- I wonder if this may be happening to you, with mill scale.

Gotta say I'm a little concerned you're using a new process to build a weight-bearing, possibly overhead storage rack. Apologies in advance if you knew this already, but please get good before you build overhead structures!

[Artie F. Emm]

Forgot to ask: what's the wall thickness of your channel?

[guidoc]

Thanks for your help - that was quick. I've been reading a lot and watching a lot of how to's, but having the actual feedback on actual welds is immensely helpful.

As for safety, this isn't an overhead rack. It's for hanging paper and plastic patterns from. Total weight supported is less than 15 lbs total (if that) on the rack and it is only about 48" tall. I figured this was a good starter project since the risk was pretty low if a weld failed. I'll leave the higher risk stuff for the professionals.

The channel is 1/8 thick on the web, the ends where I'm welding are tapered and much thicker.

The flow rate is between 30 and 40 CFH. I was using a #5 cup, switched that out to a #6 and the weld looks a bit better. I made the assumption from your reply that the #5 was restricting the flow too much, so I changed to a bigger cup.

I also sanded more of the scale off between the channels and all along the fillet and that seemed to help a lot. The channels have quite the bow to them on the web, so I don't think I'll be able to close that gap completely. I think I underestimated the amount of prep. The surface is pretty rough and I would need to remove what feels like a lot of material to get the scale off completely. I made sure the fillet at the actual weld was fresh metal. If this was mig, I would just clamp it and go.

I also upped the amps from 100 to 150 and I got a much better burn in. I also found out that the rod I was using wasn't ER70S-2. It was silicon bronze that got accidentally put in the wrong tube. I didn't notice when I first picked up the rod - it came from the tube looked copper colored, so I just assumed it was the proper rod. Chalk that one up to a learning experience.

Thanks again for your help!

[Poland308]

Sounds like you have it under control. For something like that I would be in the 130-150 amp range as well. I would probably be useing a 7 or 8 cup with my cfh around 20-25.

[exnailpounder]

Looks much better. I have grabbed silicon bronze rod by mistake before too...I thought that first "weld" looked awfully familiar. Looks like you have some tig skills goin on there. Show us the completed rack.

[Artie F. Emm]

Good on ya, that's looking much better.

[guidoc]

getting better...These are leveling feet. Sanded off the zinc from the nut to weld it.

I'm having trouble going over the tacks - just need some practice with getting the rhythm of the rod.

[exnailpounder]

Not bad at all! When I weld square tube, I usually make my tacks in the corners so the open runs will be pretty. You can also try speed tacking which makes your tacks very small and you can go over them easily and not so noticeable. Based on the corners on that tube, it looks like 1/4" wall ...just curious what amps you're running but you are well on your way.

[guidoc]

The tubing is 3/16 thick. I'm about 190 amps. Seem about right?

I find there is a huge difference between the hot rolled c channel and the tube. the tube seems very forgiving and it forms a nice puddle.

I find the filler rod "sticks" a bit when I dip it. My hands are very tired, so I noticed I've been dragging the filler in the joint to keep it steady. Is this "proper" or should the filler be "in the air" when I dip it? Same goes with the torch - I've been dragging the cup a lot because my hands are not used to holding the torch for so long.

[guidoc]

Not bad at all! When I weld square tube, I usually make my tacks in the corners so the open runs will be pretty. You can also try speed tacking which makes your tacks very small and you can go over them easily and not so noticeable. Based on the corners on that tube, it looks like 1/4" wall ...just curious what amps you're running but you are well on your way.

Thanks! - I've been at it an entire day and a half now. Sometimes the welds come out clean, sometimes not so much.

I'll have to try the speed tacks next time. I was making the tacks quite large because I am going to dry fit everything together before running the beads and I didn't want the whole thing breaking apart.

[exnailpounder]

Not bad at all! When I weld square tube, I usually make my tacks in the corners so the open runs will be pretty. You can also try speed tacking which makes your tacks very small and you can go over them easily and not so noticeable. Based on the corners on that tube, it looks like 1/4" wall ...just curious what amps you're running but you are well on your way.

Thanks! - I've been at it an entire day and a half now. Sometimes the welds come out clean, sometimes not so much.

I'll have to try the speed tacks next time. I was making the tacks quite large because I am going to dry fit everything together before running the beads and I didn't want the whole thing breaking apart.

I hear you on the tacks breaking lol. For your time spent tigging, you are doing incredibly well. You must be one of those hands-on learners. I can watch videos all I want but I never get the gist of things until I hold it in my hand. I was the kid who had to learn the hard way when my mom told me the stove was hot Great job!

[Artie F. Emm]

I find the filler rod "sticks" a bit when I dip it. My hands are very tired, so I noticed I've been dragging the filler in the joint to keep it steady. Is this "proper" or should the filler be "in the air" when I dip it? Same goes with the torch - I've been dragging the cup a lot because my hands are not used to holding the torch for so long.

"Dragging the filler" might be analogous to the lay wire technique: video here.
http://www.weldingtipsandtricks.com/how ... -wire.html

Dragging the cup might be walking the cup: video here.
http://www.weldingtipsandtricks.com/wal ... nique.html